That's fair, but for a guy who's going to get life any day not inside is a win.
They keep saying they have him boxed in and it's a matter of time, but he keeps appearing outside their perimeter. He's going to get a vehicle eventually. If he can get to the other side of Rt. 1 (which is basically the other side of Longwood Gardens from where they keep spotting him) the population density goes up significantly. Harder to hide, but easier to blend in or get a car. Lots of shopping centers, businesses, gas stations, lots more houses and frankly some of that is on his current side of Rt. 1 just past the Gardens.
Why I mentioned about the weather this afternoon was it was an opportunity for him to move. Much lower visibility for people on the ground, no helicopters or drones operating, lots of noise so it would be harder to hear him clambering around, the rain would wash his scent off things so the dogs would struggle to follow him after the rain stopped. If he was going to get out of the perimeter in a significant way, this afternoon was a big chance to do so.